Prefabricated structure and method of construction

ABSTRACT

Disclosed is a monolithic prefabricated structure that is wind and impact resistant. This special pre-cast lightweight concrete structure is a blend of special aggregates and additives combined to resist the impacts of flying debris and extremes of weather. The curved exterior surface minimizes wind friction and deflects debris. The circular structure has a low center of gravity and firm attachment to a floor made of concrete. It has protected ventilation openings, viewing ports and a strong smooth-fitting door.

BACKGROUND OF THE INVENTION

[0001] U.S. Pat. No. 6,253,655 discloses a method of making an armor to resist projectiles, with a foam plastic inner layer that absorbs energy during impacts. The same principle is applied in the present invention, with notable contrasts in the simplicity of the design, methods of construction and configuration of the final product.

[0002] U.S. Pat. No. 6,240,686 teaches that foam plastic blocks can be effectively arranged to support building loads. The invention requires the use of tensioning skins and includes multiple joints that are avoided in the present invention.

[0003] U.S. Pat. No. 6,218,002 discloses a concrete mixture containing a barrel shaped polystyrene bead as the aggregate. The concrete in this formulation contrasts with the present invention. It uses only one size of virgin polystyrene beads while the present invention uses recycled aggregates of varied sizes, allowing small particles to fill voids between larger particles and contribute to the resiliency of the structure.

[0004] U.S. Pat. No. 6,151,841 discloses a pyramid shaped shelter that is erected above ground with Plexiglas(TM) windows. The shelter demonstrates the merits of triangular sides in resisting wind, but it fail to address the problem of joints, which are eliminated in the present invention.

[0005] U.S. Pat. No. 6,131,343 discloses a parabolic-like shaped dome shelter that may be constructed of or covered with corrugated metal. This patent teaches the value of dome shapes in resisting wind, but it does not provide the simplicity, insulation and other attributes of the present invention.

[0006] U.S. Pat. No. 5,953,866 discloses a storm shelter that is partly buried underground with provisions for an emergency jack to forcibly open the sliding door. It is an attribute of the present invention that it is located above ground and is less likely to entrap occupants. In addition, ordinary carpenter tools can be used to cut an emergency escape if the door becomes inoperable. This feature does not diminish the fact that the lightweight concrete in the present invention resists severe impacts, including bullets.

[0007] U.S. Pat. No. 4,879,855 discloses a building method that incorporates polystyrene in structure walls. Walls built with this method perform satisfactorily in extreme wind conditions, but failures have occurred at wall-roof intersections. In addition, the foam plastic produces toxic gasses when exposed in building fires. The concrete in the present invention is remarkably fire proof and the design eliminates joining problems and most of the concrete required in U.S. Pat. No. 4,879,855. In the present invention polystyrene beads are coated with a formulation to create a lightweight material that performs all of the functions of the heavy concrete and steel in the above-cited patent.

[0008] People living in undeveloped and developed countries occupy structures, including emergency shelters, that are vulnerable to collapse and wind-blown missile penetration during extreme wind conditions. Few residential structures are designed to resist the highest velocity winds, and every year injuries and death occur due to intrusion of flying objects and building collapse. Shelters made of steel and concrete are often placed at floor level or below the floors inside residences. These shelters save lives, but they have recognized disadvantages. Their cost exceeds the budget limitations of many families, and occupants may be trapped under collapsed building materials. Underground shelters require expensive excavation and forming, and occupants are sometimes at risk from flooding. Stairways take up shelter space and they are inconvenient and dangerous. Typical engineering techniques used to design shelters ignore such risks and concentrate on overcoming maximum hurricane or tornado wind pressures. Structures are built with a safety factor that proves to be inadequate when the siding and roof assemblies separate and crash into adjacent property and when they collapse under loads of debris carried onto them by high winds.

[0009] In this invention less dense materials create a structure that exceeds the performance of typical shelters. This is accomplished by a smooth exterior design that prevents the wind, regardless of velocity or direction, from achieving a direct hit. Most flying objects glance off the structure in this invention without imposing the shocks felt by conventional shelters. Direct hits by lengths of 2×4 lumber moving at 150 miles per hour do not penetrate this structure. Unlike steel, the lightweight concrete in this invention has a low coefficient of thermal expansion. It does not rust, decay when exposed to below-ground moisture, or react adversely to freeze-thaw cycling. It is a good insulator and withstands exposure to heat and flames in excess of 1700 degrees F.

SUMMARY OF THE INVENTION

[0010] It is thus an object of this invention to provide a low cost structure that is safe during extreme weather, durable and easily transported. This invention, because of its superior shape, material formulation, manufacturing method and door design meets the objectives.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an elevation view of the shelter.

[0012]FIG. 2 is a view of the shelter dome showing the radio antenna, ventilation ports, interior diverters and debris collection bags.

[0013]FIG. 3 is a view of the shelter dome from directly above showing ventilator port openings.

[0014]FIG. 4 is a view of the preferred tie-down method.

[0015]FIG. 5 is a view of an alternate tie-down method.

[0016]FIG. 6 is a view of the molds used to construct the structure.

[0017]FIG. 7 is a view of the shelter floor with a ramp for handicapped access.

[0018]FIG. 8 is a view of the sliding door mechanism with the door opened to the inside.

[0019]FIG. 9 is a view of the sliding door mechanism with the door opening to the outside.

[0020]FIG. 10 is a view of the door latching mechanism in the open or unlatched position.

[0021]FIG. 11 is a view of the door latching mechanism in the closed or latched position.

[0022]FIG. 12 is a view of the door hardware and overhead track mechanism.

[0023]FIG. 13 is a view of the latching mechanism isolated on the door.

DETAILED DESCRIPTION OF THE INVENTION

[0024] This description provides illustrative information in support of the claims and should not be regarded as defining the language in the claims. Those familiar with the art will recognize that other structure dimensions and variations in shape of the dome and in the concrete mix design are within the scope of this invention.

[0025]FIG. 1 illustrates a monolithic dome-shaped structure 1 with the general location of the door latches and catches 4, some of the air vents 2 and viewing ports 3. The lightweight concrete comprising this structure provides extraordinary resistance to weather and the impacts of wind driven objects. The shape of the structure and the smooth exterior finish 1 minimize wind friction. These features and the large area of contact at the base work together to resist overturning. The viewing ports 3 are made of heavy transparent plastic or glass to allow safe viewing.

[0026]FIG. 2 displays a cutaway section of the domed roof with ventilation ports 7. These ports are nominally 2 inch diameter pipes made of plastic or steel. They replace larger window-like vents normally used. The number of vents is determined by the size of the structure and occupant load. Sufficient vents 7 to sustain healthy breathing conditions and equalize interior air pressure with outside atmospheric pressure can be easily installed by boring holes in the shelter. Because of their small diameter multiple vent pipes do not impair the structural integrity or smoothness of the structure's exterior. The pipes 7 are inclined upward from the outside to reduce infiltration by water and to provide drainage. Removable diverters 8 are connected to the vent pipes 7 on the inside. The sharp angles of the diverters 8 and the small diameter of the pipes reduce air velocity and prevent all but the smallest flying objects from entering the structure. Fine debris is caught in removable bags 6 that are permeable to admit required airflow. The bags serve as visual indicators of air movement and pressure conditions. The bags 6, diverters 8 and pipes 7 can be easily cleaned. A radio antenna 9 allows one-way or two-way communications depending on the type of receiver-transmitter 10 selected. The antenna 9 penetration through the roof is sealed to prevent water intrusion.

[0027]FIG. 3 is an overhead view illustrating the preferred placement of ventilation ports 12 below the top of the domed roof 11 and the radio antenna 13. The door 14 is equipped with hinging and latching devices of sufficient strength to develop wind and impact resistance equal to other parts of the structure. In this view the door 14 slides into the structure to open and outward to close. In this configuration the door temporarily occupies interior space. It provides protection against weather during closing.

[0028]FIG. 4 illustrates the preferred tie-down method with the bent ends 20 of ½ inch diameter anchor bolts 18 embedded in the concrete floor 19 and the threaded ends penetrating the structure near the base. Tamper-proof nuts 17 protect against vandalism and provide the structure with resistance against uplift and overturning during the most severe winds. The anchor bolts 18 are inserted through the holes in the base of the wall prior to pouring the concrete floor 19. Large washers 16 and tamper-proof nuts 17 are installed after the concrete floor is cured.

[0029]FIG. 5 illustrates an alternate tie-down method. Holes large enough to permit insertion of ½ inch diameter bolts are provided at a minimum of 8 locations around the perimeter at the base of the structure. After the structure is permanently placed on the ground the inside wall serves as a form for pouring the concrete floor 28 that has nominal compressive strength of 2500 PSI. An L-shaped anchor bolt 27 is placed vertically in the wet concrete adjacent to each hole in the structure base. 3-inch by 3-inch slotted angle plates 26 are placed over the anchor bolts 27 and the horizontal wall bolts 25. On the exterior large washers 22 are placed over the bolts to distribute the load on the lightweight concrete. Tamper-proof nuts 23 permanently attach the wall to the concrete floor.

[0030]FIG. 6 illustrates the method of forming and pouring the lightweight concrete to construct the monolithic structure. In the preferred embodiment the dome-shaped lower mold 29 is inverted and coated on the interior surface with form-release material. Cured spacer blocks 31 six inches thick made of the lightweight concrete are secured along the sides of the mold. One block 32 is secured to the bottom of the mold at the center. These blocks are identical in composition to the lightweight concrete comprising the rest of the shelter. They bond to it and become part of the structure. The lower mold 29 is partially filled with the fluid lightweight concrete creating a reservoir. A second upper mold 34 six inches smaller in diameter but identical in shape to the lower mold is forced down into the fluid concrete, descending until it rests on the center spacer block 32 and against the other spacer blocks 3l. The pressure of the upper mold 34 pressing into the fluid concrete 33 is sufficient to cause it to rise and fill the six inch space between the two molds. Vibrators are applied to the outside of the lower mold and the inside of the upper mold to cause fine particles to accumulate against the molds, creating smooth surfaces. After sufficient curing the upper mold 34 is pulled up and out of the inverted structure. The lower mold 29 and the rigid structure are inverted together so the structure is resting on its base. The lower mold 29 is then removed from the outer surface of the structure, completing the process.

[0031]FIG. 7 is a side view with a shelter wall segment showing the handicapped access ramp 36. A ramp is required because the door entrance is nominally 4 inches above ground level 39. Flexible gaskets 37 attached to grooves in the floor and in the bottom of the door compress against mating gaskets to prevent water intrusion. In a typical environment the concrete floor and handicapped access ramp are poured on solid natural ground 39. If installed on flood plains the structure must be placed on elevated ground.

[0032]FIG. 8 is a view of the shelter door 40 and the operating mechanism used to open the door to the inside. The door 40 is a cutaway segment of the structure wall 41. The top of the door is connected to 2 Unistrut(TM) tracks 44 that are attached by 2 brackets 47 to the roller assemblies 42. The rollers run inside the track and cannot be derailed. Two flat plate brackets 47, one on each face of the door are attached with bolts on each upper corner of the door. The roller assemblies 42 are equipped with ball bearings. The rollers 42 align the door 40 for precise fit against the gaskets 43 surrounding the door. The bottom door control assembly consists of notched ball bearing-equipped rollers 45 fitted onto 90 degree steel angle tracks 46 secured to the concrete floor with the v facing upward and the open angle down. Notched rollers 45 fit precisely over the steel angle tracks to control the position of the door and share the weight with the upper track and roller assembly. All door edges and mating structure surfaces are equipped with flexible gaskets 43 that firmly seal the door. The upper track assembly 44 is located above the door opening to provide head clearance to standing shelter occupants. The lower track assembly 46 is configured to allow passage of wheel chairs.

[0033]FIG. 9 is a view of the door and door operating mechanism with the door configured to be opened by moving it to the outside. This configuration may be selected in low wind areas. This configuration avoids temporary loss of interior space caused by the door opening in, but it causes the door and the upper track assembly 53 to be exposed to wind-driven debris. The lower 58 and upper 53 track mechanisms are identical to the track mechanisms in FIG. 8 except for being extended outside. The tracks holding the door are supported on the inside by two columns 55 made on fiberglass, pvc pipe or other material that is non conductive to avoid risk from lightening strikes. In this configuration the ramp 60 on one side of the shelter provides handicapped access to the structure. When closed, as shown in lighter color, the door 56 is held by 2 heavy latches 52, one on each side of the door. The latches can be operated from inside or outside of the structure. These latches 52 consist of steel plates mounted on ½ inch diameter bolts fitted through pipes penetrating the door to form bearings. The lower roller assembly 54 consists of notched rollers fitted over angle tracks 58. The door closes against replaceable gaskets 57 firmly sealing all edges.

[0034]FIG. 10 is a view of the door 63 and its 2 latch assemblies in the open or unlatched position. These latches 61 consist of ¼ inch thick steel plates nominally 4 inches wide and 8 inches long. 4 identical latches are used, 2 on the inside and 2 on the outside of the door 63. 2 pipes the same thickness as the door are inserted through a close fitting hole in the door and a ½ inch diameter steel bolt threaded on both ends is fitted through the pipe creating a bearing. The bolt is firmly attached to the latch plates 61. Catches 62 are installed on the shelter walls 64 adjacent to the door on both sides. This configuration allows easy rotation of the latches which are operable from inside or outside of the structure.

[0035]FIG. 11 is a view of the door and its latch assembly 65 in the closed position. The latch is easily operated from either the inside or outside by grasping the latch handle 67 and turning the latch to a horizontal position inside the catch plate. Replaceable gaskets where the door closes 68 into the structure wall provide weatherproof seals.

[0036]FIG. 12 is a view of the door and overhead track assembly 70 with material above the door cut away to show the tracks 70. Also shown are overhead rollers 71, door hanging brackets 72, outside catches, 73 and outside latches 74. The door 75 is carried on the rollers 71 to a distance of required opening, such as three feet into the shelter. The door is carried out to close against flexible gaskets on all edges 76.

[0037]FIG. 13 is a view of the two latch plates 78 showing a door segment 77, the bearing pipe 79 and latch bolt 80. 

What is claimed is:
 1. A prefabricated monolithic impact and wind resistant structure with a smooth dome-like shape and a low center of gravity, said structure being capable of remaining in place and providing a safe environment to occupants during the most severe weather.
 2. The provisions of claim 1, wherein the structure is constructed of concrete containing by volume 7 parts polystyrene aggregates of varied sizes smaller than ⅝ inch cubed, 3 parts Portland cement, polyacrylonitrile homopolymer or other fibers, acrylic, ethylene vinyl acetate terpolymer, styrene butadiene or other polymers, minor amounts of other additives such as fly ash and silica fume and water to allow workability.
 3. The provisions of claim 2, wherein the structure is molded by placing fluid concrete in a bowl-shaped mold and a second smaller mold being forced downward into the first mold to a controlled point of descent, said process forcing sufficient fluid concrete into the spaces between the two molds to fill the spaces and after curing complete the formation of the monolithic structure.
 4. The provisions of claim 2, wherein the structure is molded by filling a space defined by spacer blocks made of the lightweight concrete by pumping, pouring, injecting or otherwise filling the space between 2 molds and defining the shape of the structure.
 5. The provisions of claim 2, wherein the concrete is molded into a monolithic shell being six inches thick and not less than 6 feet in diameter, with the height not exceeding the base diameter.
 6. The provisions of claim 2, wherein the structure is enlarged, with uniform or non uniform thickening of the concrete in accordance with engineering calculations that determine thickness required to support increased loads imposed by increased spanned distances.
 7. The provisions of claim 1, wherein the structure with a base diameter or 8 feet or less can be easily transported and installed on reasonably level ground without site grading.
 8. The provisions of claim 1, wherein the structure is provided with a ventilation system, said system consisting of a plurality of small diameter pipes capable of transferring sufficient fresh air to sustain healthy interior conditions for the maximum number of shelter occupants during sustained occupancy and said ventilation system being capable of equalizing interior and exterior atmospheric pressures while preventing the entrance of wind blown objects.
 9. The provisions of claim 1, wherein the monolithic structure has a plurality of viewing ports consisting of solid transparent plastic or glass fitting into holes in the structure walls so as to allow viewing in at least 4 directions while protecting the viewers from flying objects.
 10. The provisions of claim 1 wherein the structure has a doorway cut out of the wall material, said cut doorway being tapered to provide firm seating when closed into its original position in the wall, and said door being sealed with gaskets to prevent water intrusion and latched to resist severe wind pressures and impact loads when closed.
 11. The provisions of claim 10, wherein the door opens toward the inside and closes toward the outside by use of an inside track mechanism that supports and guides the door, said mechanism consisting of interior overhead and bottom track assemblies equipped with ball bearing rollers.
 12. The provisions of claim 10, wherein the door opens toward the outside and closes toward the inside by use of an outside track mechanism that supports and guides the door, said mechanism consisting of exterior overhead and bottom track assemblies equipped with ball bearing rollers, and said track mechanism being supported by 2 columns inside the structure, said columns being made of materials that do not conduct electricity.
 13. The provisions of claim 1 wherein the structure has a tie-down method comprising a plurality of holes near the base, said holes allowing the insertion of horizontal anchor bolts from the inside to the outside prior to pouring of the concrete floor, and said bolts penetrating through the wall a sufficient distance to accept a washer and a fully threaded nut.
 14. The provisions of claim 1 wherein the structure is tied down by use of anchor bolts set vertically in the wet concrete floor, said vertical bolts extending through a slotted steel angle plate, and said plate receiving a second horizontal bolt penetrating the structure near the base, and washers and tamper proof nuts being installed on the horizontal bolts.
 15. The provisions of claim 1, wherein the structure is held down by being placed a minimum of four inches above the bottom of a circular trench that is at least 12 inches deep and 18 inches wide at the top, and the lower base of the structure being fully embedded in the wet concrete on both the interior and exterior sides by filling the trench with concrete, said method eliminating anchor bolts.
 16. The provisions of claim 1, wherein the structure withstands impact loads such as lumber driven by wind at the velocity of 150 miles per hour.
 17. The provisions of claim 2, wherein the polystyrene aggregates consist of recycled waste. 